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AIIMS AIIMS Solved Paper-2010

  • question_answer
    The correct order of basic strength of \[C{{H}_{3}}N{{H}_{2}}(I),\] \[{{(C{{H}_{3}})}_{2}}NH(II),\]  \[{{(C{{H}_{3}})}_{3}}N(III),\] \[{{C}_{6}}{{H}_{5}}C{{H}_{2}}N{{H}_{2}}\] in gaseous phase is

    A) \[IV<III<II<I\]   

    B) \[IV<III<I<II\]   

    C) \[I<II<III<IV\]   

    D) \[IV<I<II<III\]

    Correct Answer: D

    Solution :

    In gaseous phase, the basic strength of alkyl amines follows the following order \[{{3}^{o}}>{{2}^{o}}>{{1}^{o}}\] This is because of the presence of electron releasing \[-C{{H}_{3}}\] group which increases the electron density over nitrogen and thus, makes the more availability of lone pair for donation. Hence, the correct order of basic strength is \[\underset{(III)}{\mathop{{{(C{{H}_{3}})}_{3}}N}}\,>\underset{(II)}{\mathop{{{(C{{H}_{3}})}_{2}}NH}}\,>\underset{(I)}{\mathop{C{{H}_{3}}N{{H}_{2}}}}\,\]                                            \[\underset{(IV)}{\mathop{>\underset{\begin{smallmatrix}  (because\,of\,electron\, \\  withdrawing\,Ph\,\,group) \end{smallmatrix}}{\mathop{{{C}_{6}}{{H}_{5}}C{{H}_{2}}N{{H}_{2}}}}\,}}\,\]


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